Odtbrain

- docs: minor update and add changelog

- fix: Allow sinogram data type other than complex128
- docs: Add example with experimental data (3)
- ci: automated deployment with travis-ci

- BREAKING CHANGES:
- Dropped support for Python 2
- Renamed `sum_2d` to `integrate_2d`
- Refactoring (4, 5):
- Moved each reconstruction algorithm to a separate file
- Modified code to comply with PEP8
- Moved long doc strings from source to docs directory
- Migrate from unwrap to scikit-image
- Cleaned up example scripts
- Bugfixes:
- Mistake in "negative-modulo" method for determination of
2PI sinogram phase offsets

- Updated documentation
- Cleaned up examples

- Move documentation from GitHub to readthedocs.io
- Add universal wheel on PyPI
- Update tests on travis with new versions of NumPy

- Bugfixes:
- size of reconstruction volume in z too large for cases where
the y-size is larger than the x-size of the sinogram images
- `backpropagate_3d_tilted` used wrong shape of projections
- 3D backpropagation methods did not use power-of-two padding size